Our program continues to investigate means of presentation of medical images from a wide range of imaging modalities. The research, involving six projects and two cores, concerns techniques and clinical applications of 3D and 2D display for diagnosis and the planning of radiotherapy. Investigations into object definition and human vision develop models and methods supporting display technique development. In the 3D display area, 1) we will develop techniques for 3D exploration of medical image data and for visualization of complicated combinations of anatomy and planning objects, and 2) we will investigate 3D display applications in radiotherapy and pathology. In our 2D display work, 1) we will evaluate diagnostic uses of contrast improvements of mammographic, radiotherapy portal, and CT chest images, and b) we will develop and evaluate clinically usable diagnostic workstations in the field and in the laboratory, for both multimodality and mammographic display. Both our human vision project and our object definition project will focus on shape- and grouping-based perception and analysis in the complicated contexts found in medical images and will produce models of vision of shape. The object definition project will include application in both interactive 3D display and automatic, on-line analysis of radiotherapy portal images. Controlled evaluations will be conducted in all of the project areas. A statistics core will not only provide designs and data analyses for observer experiments but also development of improved statistics or analyses in observer studies with small samples of correlated observations, both where perceivability is rated and where continuous responses are give. The research results will allow smaller samples to provide guaranteed type I error rates and statistical power. A facilities core will support software and hardware facilities, administration, and ergonomic consultation.